System for additive manufacturing

ABSTRACT

A system is disclosed for additively manufacturing a composite structure. The system may include a support, and a print head connected to and moveable by the support. The print head may have an outlet configured to discharge a continuous reinforcement at least partially coated in a matrix, and a device located inside the print head and configured to at least partially coat the continuous reinforcement with the matrix. The system may also include a sensor configured to generate a signal indicative of an amount of the matrix, and a controller in communication with the sensor and the device. The controller may be configured to direct a command to the device to cause the device to advance matrix toward the continuous reinforcement during passage of the continuous reinforcement through the print head, and to selectively adjust the command based on the signal.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/596,397 that was filed on Oct. 8, 2019, which is based on and claimsthe benefit of priority from U.S. Provisional Application No. 62/751,461that was filed on Oct. 26, 2018, the contents of all of which areexpressly incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to a manufacturing system and,more particularly, to a system for additively manufacturing compositestructures and a method of operating the system.

BACKGROUND

Continuous fiber 3D printing (a.k.a., CF3D®) involves the use ofcontinuous fibers embedded within a matrix discharging from a moveableprint head. The matrix can be a traditional thermoplastic, a powderedmetal, a liquid resin (e.g., a UV curable and/or two-part resin), or acombination of any of these and other known matrixes. Upon exiting theprint head, a head-mounted cure enhancer (e.g., a UV light, anultrasonic emitter, a heat source, a catalyst supply, etc.) is activatedto initiate and/or complete curing of the matrix. This curing occursalmost immediately, allowing for unsupported structures to be fabricatedin free space. When fibers, particularly continuous fibers, are embeddedwithin the structure, a strength of the structure may be multipliedbeyond the matrix-dependent strength. An example of this technology isdisclosed in U.S. Pat. No. 9,511,543 that issued to Tyler on Dec. 6,2016 (“the '543 patent”).

Although CF3D® provides for increased strength, compared tomanufacturing processes that do not utilize continuous fiberreinforcement, improvements can be made to the structure and/oroperation of existing systems. For example, achieving a precisematrix-to-fiber ratio may be critical in some applications and difficultto control with existing processes and systems. Too much or too littleresin may result in a weak, brittle, flexible, and/or heavy structure.The disclosed additive manufacturing system and method are uniquelyconfigured to provide these improvements and/or to address other issuesof the prior art.

SUMMARY

In one aspect, the present disclosure is directed to a system foradditively manufacturing a composite structure. The system may include asupport, and a print head connected to and moveable by the support. Theprint head may have an outlet configured to discharge a continuousreinforcement at least partially coated in a matrix. The system may alsoinclude at least one doser located inside the print head and configuredto at least partially coat the continuous reinforcement with the matrix,a sensor located downstream of the at least one doser and configured togenerate a signal indicative of an amount of matrix coating thecontinuous reinforcement, and a controller in communication with thesensor and the at least one doser. The controller may be configured todirect a feedforward command to the at least one doser to cause the atleast one doser to advance matrix toward the continuous reinforcementduring passage of the continuous reinforcement through the print head,and to selectively adjust the feedforward command based on the signal.

In another aspect, the present disclosure is directed to a method ofadditively manufacturing a composite structure. The method may includeadvancing a matrix toward a continuous reinforcement inside of a printhead, discharging a material including the continuous reinforcement atleast partially coated in the matrix from the print head, and moving theprint head while discharging the material. The method may also includegenerating a signal indicative of an actual matrix-to-continuousreinforcement ratio of the material discharging from the print head,generating a feedforward command associated with advancing the matrixbased on a desired matrix-to-continuous reinforcement ratio of thematerial discharging from the print head, and selectively adjusting thefeedforward command based on the signal.

In yet another aspect, the present disclosure is directed to anothermethod of additively manufacturing a composite structure. This methodmay include advancing a matrix toward a continuous reinforcement insideof a print head, discharging a material including the continuousreinforcement at least partially coated in the matrix from the printhead, and moving the print head while discharging the material. Themethod may also include generating a signal indicative of an actualmatrix-to-continuous reinforcement ratio of the material dischargingfrom the print head, and generating a feedback command associated withadvancing the matrix based on a desired matrix-to-continuousreinforcement ratio of the material discharging from the print head andbased on the signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric illustration of an exemplary disclosed additivemanufacturing system; and

FIG. 2 is a schematic illustration of an exemplary disclosed print headthat may be utilized with the additive manufacturing system of FIG. 1.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary system 10, which may be used tocontinuously manufacture composite structures 12 having any desiredcross-sectional shape (e.g., circular, rectangular, or polygonal).System 10 may include at least a support 14 and a head 16. Head 16 maybe coupled to and moved by support 14. In the disclosed embodiment ofFIG. 1, support 14 is a robotic arm capable of moving head 16 inmultiple directions during fabrication of structure 12, such that aresulting longitudinal axis (e.g., a trajectory) of structure 12 isthree-dimensional. Support 14 may alternatively embody an overheadgantry or a hybrid gantry/arm also capable of moving head 16 in multipledirections during fabrication of structure 12. Although support 14 isshown as being capable of 6-axis movements, it is contemplated that anyother type of support 14 capable of moving head 16 in the same or adifferent manner could also be utilized. In some embodiments, a drivemay mechanically couple head 16 to support 14, and include componentsthat cooperate to move portions of and/or supply power to head 16.

Head 16 may be configured to receive or otherwise contain a matrix(shown as M in FIG. 2). The matrix may include any type of matrix (e.g.,a liquid resin, such as a zero-volatile organic compound resin, apowdered metal, etc.) that is curable. Exemplary resins includethermosets, single- or multi-part epoxy resins, polyester resins,cationic epoxies, acrylated epoxies, urethanes, esters, thermoplastics,photopolymers, polyepoxides, thiols, alkenes, thiolenes, and more. Inone embodiment, the matrix inside head 16 may be pressurized, forexample by an external device (e.g., by an extruder or another type ofpump—not shown) that is fluidly connected to head 16 via a correspondingconduit (not shown). In another embodiment, however, the pressure may begenerated completely inside of head 16 by a similar type of device. Inyet other embodiments, the matrix may be gravity-fed into and/or throughhead 16. For example, the matrix may be fed into head 16, and pushed orpulled out of head 16 along with one or more continuous reinforcements(shown as R in FIG. 2). In some instances, the matrix inside head 16 mayneed to be kept cool and/or dark in order to inhibit premature curing orotherwise obtain a desired rate of curing after discharge. In otherinstances, the matrix may need to be kept warm for similar reasons. Ineither situation, head 16 may be specially configured (e.g., insulated,temperature-controlled, shielded, etc.) to provide for these needs.

The matrix may be used to coat any number of continuous reinforcements(e.g., separate fibers, tows, rovings, socks, and/or sheets ofcontinuous material) and, together with the reinforcements, make up aportion (e.g., a wall) of composite structure 12. The reinforcements maybe stored within (e.g., on one or more separate internal spools—notshown) or otherwise passed through head 16 (e.g., fed from one or moreexternal spools—not shown). When multiple reinforcements aresimultaneously used, the reinforcements may be of the same materialcomposition and have the same sizing and cross-sectional shape (e.g.,circular, square, rectangular, etc.), or a different materialcomposition with different sizing and/or cross-sectional shapes. Thereinforcements may include, for example, carbon fibers, vegetablefibers, wood fibers, mineral fibers, glass fibers, metallic wires,optical tubes, etc. It should be noted that the term “reinforcement” ismeant to encompass both structural and non-structural types ofcontinuous materials that are at least partially encased in the matrixdischarging from head 16.

The reinforcements may be exposed to (e.g., at least partially coatedwith) the matrix while the reinforcements are inside head 16, while thereinforcements are being passed to head 16, and/or while thereinforcements are discharging from head 16. The matrix, dryreinforcements, and/or reinforcements that are already exposed to thematrix may be transported into head 16 in any manner apparent to oneskilled in the art. In some embodiments, a filler material (e.g.,chopped fibers) may be mixed with the matrix before and/or after thematrix coats the continuous reinforcements.

One or more cure enhancers (e.g., a UV light, an ultrasonic emitter, alaser, a heater, a catalyst dispenser, etc.) 18 may be mounted proximate(e.g., within, on, or adjacent) head 16 and configured to enhance a curerate and/or quality of the matrix as it is discharged from head 16. Cureenhancer 18 may be controlled to selectively expose portions ofstructure 12 to energy (e.g., UV light, electromagnetic radiation,vibrations, heat, a chemical catalyst, etc.) during material dischargeand the formation of structure 12. The energy may trigger a chemicalreaction to occur within the matrix, increase a rate of the chemicalreaction, sinter the matrix, harden the matrix, or otherwise cause thematrix to cure as it discharges from head 16. The amount of energyproduced by cure enhancer 18 may be sufficient to cure the matrix beforestructure 12 axially grows more than a predetermined length away fromhead 16. In one embodiment, structure 12 is completely cured before theaxial growth length becomes equal to an external diameter of thematrix-coated reinforcement.

The matrix and/or reinforcement may be discharged from head 16 via atleast two different modes of operation. In a first mode of operation,the matrix and/or reinforcement are extruded (e.g., pushed underpressure and/or mechanical force) from head 16 as head 16 is moved bysupport 14 to create the 3-dimensional trajectory within a longitudinalaxis of structure 12. In a second mode of operation, at least thereinforcement is pulled from head 16, such that a tensile stress iscreated in the reinforcement during discharge. In this mode ofoperation, the matrix may cling to the reinforcement and thereby also bepulled from head 16 along with the reinforcement, and/or the matrix maybe discharged from head 16 under pressure along with the pulledreinforcement. In the second mode of operation, where the matrix isbeing pulled from head 16 with the reinforcement, the resulting tensionin the reinforcement may increase a strength of structure 12 (e.g., byaligning the reinforcements, inhibiting buckling, etc.), while alsoallowing for a greater length of unsupported structure 12 to have astraighter trajectory. That is, the tension in the reinforcementremaining after curing of the matrix may act against the force ofgravity (e.g., directly and/or indirectly by creating moments thatoppose gravity) to provide support for structure 12.

The reinforcement may be pulled from head 16 as a result of head 16being moved by support 14 away from an anchor point 20. In particular,at the start of structure formation, a length of matrix-impregnatedreinforcement may be pulled and/or pushed from head 16, deposited ontoanchor point 20, and cured such that the discharged material adheres (oris otherwise coupled) to anchor point 20. Thereafter, head 16 may bemoved away from anchor point 20, and the relative movement may cause thereinforcement to be pulled from head 16. It should be noted that themovement of reinforcement through head 16 could be assisted (e.g., viainternal feed mechanisms), if desired. However, the discharge rate ofreinforcement from head 16 may primarily be the result of relativemovement between head 16 and anchor point 20, such that tension iscreated within the reinforcement. It is contemplated that anchor point20 could be moved away from head 16 instead of or in addition to head 16being moved away from anchor point 20.

A controller 22 may be provided and communicatively coupled with support14, head 16, and any number of cure enhancers 18. Each controller 22 mayembody a single processor or multiple processors that are configured tocontrol an operation of system 10. Controller 22 may include one or moregeneral or special purpose processors or microprocessors. Controller 22may further include or be associated with a memory for storing data suchas, for example, design limits, performance characteristics, operationalinstructions, tool paths, and corresponding parameters of each componentof system 10. Various other known circuits may be associated withcontroller 22, including power supply circuitry, signal-conditioningcircuitry, solenoid driver circuitry, communication circuitry, and otherappropriate circuitry. Moreover, controller 22 may be capable ofcommunicating with other components of system 10 via wired and/orwireless transmission.

One or more maps may be stored in the memory of controller 22 and usedduring fabrication of structure 12. Each of these maps may include acollection of data in the form of lookup tables, graphs, and/orequations. In the disclosed embodiment, the maps may be used bycontroller 22 to determine the movements of head 16 required to producethe desired size, shape, and/or contour of structure 12, and to regulateoperation of cure enhancers 18 in coordination with the movements.

As shown in FIGS. 1 and 2, head 16 may include, among other things, anoutlet 24 and a matrix reservoir 26 located upstream of outlet 24. Inthis example, outlet 24 is a single-channel nozzle configured todischarge composite material having a generally circular, tubular, orrectangular cross-section. The configuration of head 16, however, mayallow outlet 24 to be swapped out for another outlet (e.g., an outlet ofa different configuration—not shown) that discharges composite materialhaving the same or a different shape (e.g., a flat or sheet-likecross-section, a multi-track cross-section, etc.). Fibers, tubes, and/orother reinforcements may pass through matrix reservoir 26 and be wetted(e.g., at least partially coated and/or fully saturated) with matrixprior to discharge.

In the example of FIG. 2, an exemplary wetting arrangement 28 isdisclosed for use in wetting reinforcements (shown as R) with matrix(shown as M) prior to discharge through outlet 24. In this arrangement28, matrix may be advanced (e.g., sprayed, leaked, injected, etc.) onto,into, and/or through the reinforcements via one or more dosers 30. Thismay occur at any location upstream of outlet 24, for example withinmatrix reservoir 26 or even further upstream.

In the example depicted, arrangement 28 includes at least one upstreamdoser 30 a and at least one downstream doser 30 b. Each of these dosers30 may be connected to a source (e.g., a pump) 32 of pressurized matrixand configured to selectively advance a desired quantity of the matrixtoward the passing reinforcement(s) at a desired timing and/or rate.

The advancement location(s), in some embodiments, may be associated withone or more rollers 34 (e.g., located at or immediately upstream ofroller(s) 34) that help to move the dosed matrix into and/or through thereinforcement(s). In the disclosed example, a roller 34 locatedimmediately downstream of doser 30 may be positioned to exert a pressureat a same side of the reinforcement as doser 30, thereby facilitatingmovement of the matrix through the reinforcement (e.g., by way of apressure differential through the reinforcement). It is contemplated,however, that one or more rollers 34 may be located at a side oppositedoser(s) 30, if desired. When multiple rollers 34 are utilized, rollers34 may mounted at alternating sides of the reinforcement along a lengthof the reinforcement.

In some embodiments, a wringer 36 may be provided and selectivelyactivated (e.g., by controller 22—referring to FIG. 1) to wring excessmatrix out of the reinforcement at a location downstream of doser(s) 30.Wringer 36 may take any form known in the art. In the depicted example,wringer 36 includes a roller 38 that is biased toward roller 34, suchthat the wetted reinforcement is sandwiched therebetween. The bias maybe exerted, for example, by a spring 40. In one embodiment, the bias ofspring 40 is constant. In another embodiment (shown), the bias may bevariable and regulated by controller 22. It is contemplated that spring40 may be omitted and/or replaced with an actuator such that wringer 36may be completely disengaged, if desired.

A scraper 42 may be provided in place of or in addition to wringer 36(e.g., upstream or downstream of wringer 36), in some embodiments.Scraper 42, like wringer 36, may be configured to remove excess resinfrom the wetted reinforcement. However, unlike wringer 36, the resinremoval may not be a result of reinforcement sandwiching (i.e., pressureapplication from opposing sides to remove excess internal resin).Instead, an edge of scraper 42 may scrape over an outer surface of thewetted reinforcement, thereby removing excess resin primarily from theouter surface. It is contemplated that any number of scrapers 42 may beutilized and placed at the same or opposites sides of the wettedreinforcement in a staggered arrangement. It is also contemplated thatan actuator may be associated with one or more of the scrapers 42 andregulated by controller 22 to adjust a position of scraper(s) 42relative to the wetted reinforcement.

In some applications a viscosity of the matrix may affect wetting of thereinforcement, and viscosity of the matrix can be modified by adjustinga temperature of the matrix. As shown in FIG. 2, a heater 44 may beassociated with arrangement 28 and regulated by controller 22 toselectively vary a temperature of the matrix provided by source 32 todosers 30. In the disclosed example, heater 44 includes coils placedaround a supply passage leading to source 32. It should be noted,however, that other conventional heaters may be utilized and placed inother locations within print head 16 (e.g., with a sump and/or wall ofreservoir 26).

It is contemplated that arrangement 28 may be operated in a feedforwardand/or in a feedback manner to provide a desired ratio ofmatrix-to-reinforcement at outlet 24. To provide feedforward control,controller 22 may determine an amount and/or rate of matrix that shouldbe advanced toward the passing reinforcement at a particular temperaturebased on a desired matrix-to-reinforcement ratio and given travel speedof the reinforcement through arrangement 28. Controller 22 may thenmonitor the travel speed (e.g., via an encoder associated with roller(s)34, via monitored and/or commanded movement of support 14, via anoffboard tracker, or in another manner), and selectively adjustoperation of doser(s) 30 according to a relationship map stored inmemory to advance a theoretical amount of matrix corresponding to thedesired ratio.

To provide feedback control, a sensor 46 located downstream of at leastdoser 30 a may be configured to generate a signal indicative of anactual amount of matrix incorporated into and/or encapsulating thepassing reinforcement. Sensor 46 may be, for example, an acousticsensor, an optical sensor, a camera, or another type of sensor know inthe art. The signal may be directed to and used by controller 22 toadjust actuation of doser 30 a (e.g., to advance more or less resin), 30b (e.g., to advance a trim amount of resin), wringer 36 (e.g., to wringmore or less resin out of the reinforcement), scraper(s) 42 (e.g., toscrap off more or less resin), and/or to heater 44 (or increase ordecrease heating of the resin) and thereby bring the dischargingcomposite material into check with the desired matrix-to-reinforcementratio.

INDUSTRIAL APPLICABILITY

The disclosed systems may be used to continuously manufacture compositestructures having any desired cross-sectional shape and length. Thecomposite structures may include any number of different fibers of thesame or different types and of the same or different diameters, and anynumber of different matrixes of the same or different makeup. Operationof system 10 will now be described in detail.

At a start of a manufacturing event, information regarding a desiredstructure 12 may be loaded into system 10 (e.g., into controller 22 thatis responsible for regulating operations of support 14 and/or head 16).This information may include, among other things, a size (e.g.,diameter, wall thickness, length, etc.), a contour (e.g., a trajectory),surface features (e.g., ridge size, location, thickness, length; flangesize, location, thickness, length; etc.), connection geometry (e.g.,locations and sizes of couplings, tees, splices, etc.), desired weavepatterns, weave transition locations, matrix specifications (e.g., curetemperatures), reinforcement specifications, etc. It should be notedthat this information may alternatively or additionally be loaded intosystem 10 at different times and/or continuously during themanufacturing event, if desired. Based on the component information, oneor more different reinforcements and/or matrixes may be selectivelyinstalled and/or continuously supplied into system 10.

To install the reinforcements, individual fibers, tows, and/or ribbonsmay be passed through matrix reservoir 26, over roller(s) 34, throughwringer 36, past scraper(s) 42, and through outlet 24. In someembodiments, the reinforcements may also need to be connected to apulling machine (not shown) and/or to a mounting fixture (e.g., toanchor point 20). Installation of the matrix may include filling head 16(e.g., reservoir 26) and/or coupling of an extruder (not shown) to head16.

The component information may then be used to control operation ofsystem 10. For example, the reinforcements may be pulled and/or pushedalong with the matrix from head 16. Support 14 may also selectively movehead 16 and/or anchor point 20 in a desired manner, such that an axis ofthe resulting structure 12 follows a desired three-dimensionaltrajectory. Cure enhancers 18, support motion, doser(s) 30, wringer 36,scraper 42, heater 44, and/or other operating parameters of system 10may be adjusted in real time during operation to provide for desiredbonding, strength, and other characteristics of structure 12. Oncestructure 12 has grown to a desired length, structure 12 may be severedfrom system 10.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the disclosed system andmethods. Other embodiments will be apparent to those skilled in the artfrom consideration of the specification and practice of the disclosedsystem method. It is intended that the specification and examples beconsidered as exemplary only, with a true scope being indicated by thefollowing claims and their equivalents.

What is claimed is:
 1. A system for additively manufacturing a compositestructure, comprising: a support; a print head connected to and moveableby the support, the print head having an outlet configured to dischargea continuous reinforcement at least partially coated in a matrix; adevice located inside the print head and configured to at leastpartially coat the continuous reinforcement with the matrix; a sensorconfigured to generate a signal indicative of an amount of the matrix;and a controller in communication with the sensor and the device, thecontroller being configured to: direct a command to the device to causethe device to advance matrix toward the continuous reinforcement duringpassage of the continuous reinforcement through the print head; andselectively adjust the command based on the signal.
 2. The system ofclaim 1, wherein: the device is a first device; and the system furtherincludes a second device located inside the print head and configured toadvance matrix towards the continuous reinforcement, the second devicebeing located at a different serial location relative to the firstdevice and motion of the continuous reinforcement through the printhead.
 3. The system of claim 2, further including at least one source ofpressurized matrix fluidly connected with the first and second devices.4. The system of claim 1, further including a matrix heater locatedinside of the print head.
 5. The system of claim 4, wherein thecontroller is further configured to selectively activate the matrixheater based on the signal.
 6. The system of claim 1, further includingat least one roller located inside of the print head and downstream ofthe device at a same side of the continuous reinforcement as the device.7. The system of claim 6, wherein the sensor is located downstream ofthe at least one roller.
 8. The system of claim 7, wherein: the deviceis a first device; the system further includes a second device; and theat least one roller is located serially between the first and seconddevices relative to motion of the continuous reinforcement through theprint head.
 9. A method of additively manufacturing a compositestructure, comprising: advancing a matrix toward a continuousreinforcement inside of a print head; discharging a material includingthe continuous reinforcement at least partially coated in the matrixfrom the print head; moving the print head while discharging thematerial; generating a signal indicative of an amount of the matrix; andselectively adjusting the advancing of the matrix based on the signal.10. The method of claim 9, wherein advancing the matrix includesadvancing the matrix at two locations spaced apart from each other in adirection of the continuous reinforcement moving through the print head.11. The method of claim 10, further including pressurizing the matrixand directing the pressurized matrix to the two locations.
 12. Themethod of claim 9, further including heating the matrix inside of theprint head.
 13. The method of claim 12, wherein heating the matrixincludes heating the matrix based on the signal.
 14. The method of claim9, further including pressing the matrix through the continuousreinforcement at a location inside the print head.
 15. The method ofclaim 14, wherein generating the signal includes detecting the amount ofthe matrix downstream of the location.
 16. The method of claim 10,further including pressing the matrix through the continuousreinforcement at a location inside the print head between the twolocations.
 17. The method of claim 9, further including generating apressure differential through the continuous reinforcement at a locationdownstream of where the matrix is advanced towards the continuousreinforcement.
 18. The method of claim 17, wherein generating the signalincludes generating the signal at a location downstream of the pressuredifferential.
 19. The method of claim 9, further including heating thematrix.
 20. The method of claim 19, wherein heating the matrix includesheating the matrix based on the signal.